BaseTools: add new command line option to support override PCD value

BaseTools: add new command line option to support override PCD value

this patch add new feature to support override PCD value on the command
line. The value from the command line is the highest priority.
1.Add option(--pcd) to support both PcdName and TokenSpaceGuild.PcdName
2.For void* type PCD, use following format:
  cstring PCD: --pcd PcdName="string"
  unicodestring PCD: --pcd PcdName=L"string"
  CArray PCD: --pcd PcdName=B"{0x1, 0x2}"
3.Build Report, use *B to show the PCD value was overridden in the
command line.
4.Error Condition:
Report error if the PCD is not found
Report error if the PcdName is found under multiple different TokenSpaceGuid
Report error if PCD value syntax is incorrect
Report error if void* type PCD value exceed its max size

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>